McDuffies in Holmes county

I am trying to trace my great great grandmother Penny McDuffie Melvin's parents. The closest I can find is a William and Charity McDuffie in Holmes county in 1860 census. I was told by my mother that her great great grandmother was called Mammy T which could have been Charity.The census was taken the year Penny was born so she does not show up on their household for that year.I do not know for sure if this couple were her parents but they are in the right place around the right time.Does anyone know anything about this couple or does Penny McDuffie Melvin sound familiar?